The present invention relates to a pressure fixing apparatus for electrophotography in which the pressing force applied by pressure rollers to fix a toner image to a sheet is a function of the width of the sheet.
It is well known in the art to fix a toner image to a copy sheet by feeding the sheet between pressure rollers which crush the toner particles into the sheet. The pressing force of the rollers is usually set to be sufficient for the widest sheet which the electrophotographic copying machine in which the fixing apparatus is provided can accomodate. A problem arises in that this force is too great for sheets of smaller width, resulting in crushing of the photoconductive layer on the sheets which changes the luster. For very narrow sheets, the force may be so great that the sheets will be wrinkled. Such wrinkles not only render the copy unusable but cause stress concentrations on the rollers. Such wrinkles may also cause a sheet jam necessitating partial disassembly of the apparatus to remove the jammed sheet or sheets.